Human warts (verrucae vulgares) are benign, cutaneous neoplasms induced by an oncogenic DNA virus, human papilloma virus. Little is known about the biology of warts, but infection, progression and resolution of warts apparently depends upon host immunologic responses. Studies of virion and non-virion wart-associated antigens will correlate host responses with the clinical course of the neoplasms. Wart tissues and wart-derived tissue culture cells will serve as substrates for immunologic and molecular probes in experiments designed to understand virion assembly, viral protein synthesis and the cellular integration of the viral genome. Basic investigations in the pathogenesis of warts and cutaneous viral oncogenesis may open avenues of therapy based on immunotherapy or anti-viral drugs.